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Classification of Elements and Periodicity in Properties appeared 36 times across 3 years — 4.2% of Chemistry. This question is from Periodic Trends in Properties.

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Questions 9 16 11 36
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Which of the following statements are correct? A. The process of the addition an electron to a neutral gaseous atom is always exothermic B. The process of removing an electron from an isolated gaseous atom is always endothermic C. The 1st ionization energy of the boron is less than that of the beryllium D. The electronegativity of C is 2.5 in CH₄ and CCl₄ E. Li is the most electropositive among elements of group I Choose the correct answer from the options gives below

Periodic Trends in Properties
Periodic Trends in Properties

Solution & Explanation

Core Logic

Let us check each criteria statement:

  • A is incorrect: Electron gain can be endothermic for stable configurations like noble gases or alkaline earth metals.
  • B is correct: Removing an electron from a stable atomic nucleus always requires input energy, hence Δ H > 0 (endothermic).
  • C is correct: Be (1s² 2s²) has a stable, fully-filled subshell configuration, making its first ionization energy higher than B (1s² 2s² 2p¹) where the electron is removed from a higher energy p-orbital.
  • D is incorrect: Due to inductive withdrawal and shifting effective charge distribution, electronegativity alters slightly contextually across different molecular systems (CCl₄ > CH₄).
  • E is incorrect: Cesium (Cs) is the most electropositive Group 1 element.
Step 1: Match with Choices

Statements B and C are definitively evaluated to be correct, corresponding to option (1).

Pattern Recognition

Shortcut: Ionization energy is strictly endothermic (+ Δ H). Beryllium versus Boron is a classic fully-filled subshell anomaly (IE₁ Be > B). Knowing these isolates option (1) immediately.

Chapter Mix

Class 11 Chemistry: Classification of Elements and Periodicity in Properties

More Classification of Elements and Periodicity in Properties Previous-Year Questions — Page 8

Q70 jee_main_2024_31_jan_morning Electron Gain Enthalpy
The correct sequence of electron gain enthalpy of the elements listed below is A. Ar B. Br C. F D. S Choose the most appropriate from the options given below:
  • A. C > B > D > A
  • B. A > D > B > C
  • C. A > D > C > B
  • D. D > C > B > A

Solution

Core Logic

Electron gain enthalpy (ΔegH) values are considered with their signs when ordering from largest to smallest algebraically.

ElementΔegH (kJ/mol)
F-333
S-200
Br-325
Ar+96

Arranging these algebraically from highest to lowest: +96 > -200 > -325 > -333 Thus, Ar > S > Br > F, which corresponds to A > D > B > C.

Pattern Recognition

Noble gases always have positive electron gain enthalpies (highest algebraically). Halogens have highly negative values (lowest algebraically). Fluorine is highly negative, Bromine is slightly less negative. Sulfur sits in between.

Chapter Mix

Class 11 Chemistry: Classification of Elements and Periodicity in Properties

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